lkml.org 
[lkml]   [2012]   [Jan]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] speed up /proc/pid/stat, statm
On Tue, 31 Jan 2012 12:36:12 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Tue, 31 Jan 2012 17:14:43 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> > +int seq_put_decimal_ll(struct seq_file *m, char delimiter,
> > + long long num)
> > +{
> > + if (num < 0) {
> > + if (m->count + 3 >= m->size) {
> > + m->count = m->size;
>
> Why is m->count udpated even thought we didn't write any data?
> seq_put_decimal_ull() does it too.
>

seq_xxxx functions set m->count == m->size when it finds possible buffer overflow.
If m->count == m->size after ->show(), buffer will be freed and twice size buffer
will be re-allocated, and retry.

If we don't set m->count == m->size here, following seq_putc() will succeed and
we'll see corrupted outputs.


Thanks,
-Kame



> > + return -1;
> > + }
> > + if (delimiter)
> > + m->buf[m->count++] = delimiter;
> > + num = -num;
> > + delimiter = '-';
> > + }
> > + return seq_put_decimal_ull(m, delimiter, num);
> > +
> > +}
> > +EXPORT_SYMBOL(seq_put_decimal_ll);
>



\
 
 \ /
  Last update: 2012-02-01 00:59    [W:0.040 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site